Noise suppression means



April 15, 1969;

B. EVANS NOISE SUPPRESSION MEANS Shet Filed Oct. 20,

April 15, 1969 B. EVANS NOISE'SUPPRESSIQN MEANS sheet Filed Oct. 20. 1965 FIG. 10 mvw'roa L 00f 5. [V

a m F Ah ORNEY United States Patent 3,438,330 NOISE SUPPRESSION MEANS Louis B. Evans, Afton Township, Washington County, Minn, assignor to Waterous Company, Ramsey, Minn., a corporation of Minnesota Filed Oct. 20, 1965, Ser. No. 498,438 Int. Cl. F04d N00 US. Cl. 103-113 4 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a structure for preventing the cavitation of a centrifugal pump. One or more passages are provided from the 'mouth of the impeller to the op posite side thereof which is open to all or a part of the pressure at the discharge of the impeller. In preferred form, the passage is formed by providing a groove communicating with the base of a key-way which is either in the impeller or in the supporting shaft. The arrangement is such that the groove may be formed while machining the key-way. In another form angularly spaced passages through the impeller form the connection between the high and low pressure chambers.

This invention relates to an improvement in noise suppressing means for centrifugal pumps, and deals particularly with a means of eliminating or suppressing noise due to cavitation.

In the operation of centrifugal pumps, noise sometimes occurs due to cavitation which takes place as the liquid approaches the eye of the impeller. Under certain conditions, a zone of extremely low pressure may occur adjacent to the impeller shaft, and if the pressure in the zone falls below the vapor pressure of the liquid, cavitation will result and noise and vibration will be evident. It is an object of the present invention to by-pass water to this zone so that cavitation may be eliminated or suppressed so that no noise is evident.

A feature of the resent invention resides in providing a means of directing water from a high pressure area of a centrifugal pump to the suction side thereof at a point adjacent to the impeller shaft where the zones of extremely low pressure may occur. In cenirifugal pumps which employ single-hub impellers, the result may be accomplished by providing one or more holes or fluid passages through the impeller shroud, the impeller hub, or even through the impeller shaft. Single hub impellers are impellers such as are used in pumps with a pair of similar impellers on a single impeller shaft where the axial thrust on each impeller, due to the unbalanced force of the water under high pressure on one side, is opposed by a similar force on the oiher impeller. With impellers of the single hub-type, the side of the impeller opposite the eye of the impeller is subject to elevated pressures.

A feature of the present invention resides in the fact that a somewhat different type of means may be employed to prevent cavitation at the eye of an impeller of either the single or double hub type. This means comprises a tubular connection leading from some point in the pump discharge to a point adjoining the impeller eye and through which liquid may flow under pressure to a point near the impeller shaft and adjoining the impeller eye.

These and other objects and novel features of the present invention will be more clearly and fully set forth in the following specification and claims.

In the drawings forming a part of the specification:

FIGURE 1 is a vertical sectional view through a centrifugal pump having a pair of single hubbed impellers mounted in opposed relation on a common impeller shaft, the section being a diagrammatic section to indicate the pump passages.

FIGURE 2. is an enlarged sectional detail through the hub and eye portion of the impeller.

FIGURE 3 is a sectional view through the hub portion of the impeller, the position of the section being indicated by the line 3-3 of FIGURE 2..

FIGURE 4 is a view similar to FIGURE 2 'but showing a modified form of construction.

FIGURE 5 is a vertical sectional view through the impeller illustrated in FIGURE 4, the position of the section being indicated by the line 5-5 of FIGURE 4.

FIGURE 6 is a view similar to FIGURE 2 showing another modified form of construction.

FIGURE 7 is a cross-sectional view through the hub of the impeller shown in FIGURE 6, the position of the section being indicated by the line 7-7 of FIGURE 6.

FIGURE 8 is a sectional view similar to FIGURE 2 showing another modified form of construction.

FIGURE 9 is a vertical sectional view through the hub of the impeller shown in FIGURE 8, the position of the section being indicated by the line 9-9 of FIG- URE 8.

FIGURE 10 is an enlarged vertical sectional View through another modified form of construction.

FIGURE 11 is a vertical sectional view through the axis of the propeller shaft of a modified form of pump, showing a structure such as that shown in FIGURE 10 applied to a double hub impeller pump.

The centrifugal pump A is somewhat diagrammaticallyrillustrated in FIGURE 1 of the drawings, the section indicated being designed to show portions of the pump intake and the pump discharge manifold. The pump A includes a housing 10 having aligned apertures 11 and 12 on opposite sides thereof through which an impeller shaft 13 extends. The impeller shaft 13 is supported by outboard bearings, one of which is illustrated at 14 which in turn is supported by an outboard bearing cap 15 attached to an end of the housing 10.

The housing includes a pair of vollutes 16 and 17 separated by a central partition member 19. A central sealing ring 20 is mounted in an aperture 21 in the partition wall 19, and the sealing ring closely encircles the shaft 13 to provide a separation between the two impeller chambers.

The housing 10 also includes an inlet or suction chamber on each side of the impeller chambers. A pair of impellers 23 and 24' are supported in spaced relation upon the shaft 13, the impellers being on opposite sides of the partition 19 and sealing ring 20. The eyes 25 and 26 of the impellers 23 and 24 face outwardly from one another and are in communication with the inlet or suction chamber 22. As will be understood, rotation of the impeller shaft 13 acts to force the fluid outwardly through the impellers 16 and 17 and to the pump discharge. Stufling boxes 27 are provided between each end of the pump housing 10 and the shaft 13, and guides 29 encircling the shaft 13 act to direct the fluid smoothly from the suction chamber 22 to the impeller eyes 25 and 26.

From time to time under certain operation conditions, a zone of extremely low pressure may occur adjacent to the shaft 13 or the guides 29 encircling the shaft 13. If the pressure in the zone falls below the vapor pressure of the liquid, cavitation will result, and noise and vibration will result. FIGURES 1 to 3 of the drawings show one form of construction designed to eliminate this condition.

As will be evident from the drawings, the eye portion 25 or 26 of each of the impellers 23 and 24 are sealed with respect to inwardly extending circular flanges 30 and 31 integral with the housing 10 by means of sealing and bearing rings 32 and 33 respectively. As the opposite sides of the impeller shrouds are spaced from the partition wall 19 and sealing ring 20, the areas 34 and 35 between the impellers and the central partition structure are subject to discharge pressure or at least an elevated pressure. Passages 36 and 37 are provided through the impellers in a direction generally parallel to the axis of the shaft 13. With this arrangement, liquid under pressure may flow from the higher pressure areas 34 and 35 into the eyes of the impellers near the shaft 13, the liquid flowing to the zone of low pressure at these points of the impeller eyes. As a result, a small amount of the liquid pumped will by-pass back into the eyes of the impellers at the zones of low pressure thereof. As will also be evident, the greater the difl'erential in pressure between the high pressure areas 34 and 35 and the low pressure zones in the eyes of the impeller, the greater will be the amount of liquid by-passed. The stream of liquid entering this zone eliminates or suppresses cavitation, correspondingly reducing the noise and the vibration in the pump.

The structures shown in FIGURES 4 and 5 of the drawings differs from the construction previously described only in the position of the fluid passage through the impellers, and the remaining portions of the pump have been given similar identifying numbers. In the arrangement illustrated in FIGURES 4 and 5, a channel 39 is cut through the impeller hub of the impeller 24 at the base of the key-way 40 containing the key 41 which holds the impeller 24 from rotation relative to the shaft 13. The purpose of this particular location of the channel 39 is to permit the key-way 40 and channel 39 to be formed in a single machining operation. As will be noted, the channel 39 leads from the high-pressure area 35 to the eye 26 of the impeller 24 closely adjacent the periphery of the shaft 13. During operation of the pump, the liquid under pressure is therefore by-passed into the eye of the impeller to prevent cavitation. The opposite impeller 23 may be similarly formed.

With reference now to FIGURES 6 and 7 of the drawings, it will be noted that this structure differs from the structure illustrated in FIGURES 4 and 5 only in the fact that the by-pass passage between the zone of highpressure and the zone of low-pressure extends through the shaft 13 rather than through the hub of the impeller 24. As indicated in these figures, a channel 42 is formed at the base of the keyway 43 cut in the shaft 13. An opposed key-way is formed in the impeller hub of the impeller 24 and a key 45 is provided in the key-ways to hold the impeller 24 from rotation relative to the shaft 13. As is indicated in FIGURE 6 of the drawings, the channel 42 is extended somewhat beyond the opposite sides of the hub of the impeller 24 and of the key 45 and therefore forms a communication between the high-pressure chamber 35 and the eye 26 of the impeller 24.

FIGURES 8 and 9 of the drawings show a construc tion which is very similar to that illustrated in FIGURES 2 and 3. As indicated in FIGURE 9 of the drawings, the hub of the impeller 24 is provided with a series of angularly spaced passages 46 therethrough, forming communication between the high-pressure chamber 35 on one side of the impeller and points adjacent the shaft at the eye portion 26 of the impeller. In other words, instead of having a single aperture 37 as shown in FIGURE 3, the structure shown in FIGURES 8 and 9 have a series of angulary spaced passages so that water may flow through the impeller at various points about the periphery of the hub.

The structures shown in FIGURES 10 and 11 are quite similar in nature, with the exception of the fact that FIGURE 10 shows a pump of the type which has been described and incorporating single hub impellers, while FIGURE 11 shows a pump having a double-hubbed impeller. The structure illustrated in FIGURE 11 will be first described.

The pump shown in FIGURE 11 includes an impeller of the double-hubbed type which is indicated by the numeral 47. The impeller 47 is secured by a nut 48 upon the end of an impeller shaft 49. The pump housing 50 is provided with an inlet or suction manifold 51 and an outlet or discharge passage 52. The impeller 47 is mounted in a volute 53 formed as a part of the housing 50'.

The shaft 49 extends through an opening 54 in the wall of the housing 50. Packing rings '55 encircle the shaft 49 in the opening 54 and are held in place by a packing gland 56. The packing gland 56 is supported by a pair of studs 57 extending in parallel relation from the housing 50 on opposite sides of the opening 54. Nuts 59 are engaged on the studs 57 to draw the packing gland 56 toward the packing 55.

A conduit 60 is supported at one end by a fitting 61 communicating with the pump outlet 52. The conduit 60 is also supported by a fitting 62 communicating with the intake manifold 51. An angularly turned end 63 on the conduit 60 terminates in closely spaced relation to the eye 64 of the impeller 47 closely adjacent to the end of the shaft 49.

The cylindrical forward surface 65 of the impeller 47 is sealed with respect to an inwardly extending flange 66 forming a part of the housing 50. A cylindrical flange 67 projects from the opposite side of the impeller 47 and is sealed with respect to the housing by a bearing ring 69. Thus, pressures on both sides of the impellers at equal radii are the same, so that it is not possible to bypass water from one side of the impeller to the other in the manner previously described.

In the operation of the pump, a certain amount of fluid under pressure is bypassed through the conduit 60 from the pump discharge to a point adjacent the periphery of the shaft at the eye of the impeller 47, thereby preventing or greatly reducing cavitation when low pressure is experienced at this point.

The structure shown in FIGURE 10 functions in the same manner as the structure shown in FIGURE 11. A conduit 71 leads from some point in the discharge manifold 72 and is provided with an angularly turned end 73 terminating in closely spaced relation to the eye 26 of the impeller 24. Thus, in place of providing a passage directly through the impeller shroud, the impeller hub or the impeller shaft, the fluid under pressure may bypass from the pump discharge manifold to a point closely adjoining the hub of the impeller 24 to prevent cavitation of the pump.

In accordance with the patent statutes, I have described the principles of construction and operation of my improvement in noise suppressing means for centrifugal pumps, and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that changes may be made within the scope of the following claims without departing from the spirit of my invention.

I claim:

1. A noise suppression means for centrifugal pumps including:

a pump housing,

an impeller shaft rotatably supported by said housing,

an impeller supported on said shaft within said housing and having an inlet eye,

an inlet chamber within said housing adjoining said eye,

a portion of said housing comprising a pressure chamber subject to the pressure of fluid leaving said impeller,

a pump intlet communicating with said inlet chamber and a pump outlet communicating with said pressure chamber, and

cooperable key-ways in said shaft and said impeller throughout the axial length of said impeller inwardly of said eye, said key-ways having parallel sides and a base,

a key in said keyways, and

a groove in the base of one of said key-ways through which fluid may by-pass from one side of the impeller, which forms a part of said pressure chamber to the inlet chamber side of said impeller,

said groove being narrower in width than the key-way and key.

5 6 2. The structure of claim 1 and in which said groove forms a part of said pressure chamber to the inlet is in the impeller key-way. chamber side of said impeller,

3. The structure of claim 1 and in which said groove said groove being located in a manner not to interis in the shaft key-Way. fere with the proper positioning of said key in said 4. A noise suppression means for centrifugal pumps 5 key-way. including: References Cited 3 PumP housing UNITED STATES PATENTS an impeller shaft rotatably supported by said housing, 1 946 2 an impeller supported on said shaft within said hous- 3 35; 12:83:23

ing and having an inlet eye, 1 an inlet chamber Within said housing adjoining said eye, 0 F P 103-413 a portion of said housing comprising a pressure cham- W1 lams 103*112 ber subject to the pressure of fluid leaving said im- FOREIGN PATENTS Pellerq 924,068 2/1955 Germany. a pump mlet communicatmg with said inlet chamber 15 653,243 11/1928 France and a pump outlet communicating with said pressure 972,528 10/1950, France chamber, and 1,130,511 10/1956 France. eooperable key-ways in said shaft and said impeller 697,592 10/1940 Germany throughout the axial length of said impeller inwardly 03 3 2 Great Britain ofsald y 20 735,866 3/1955 Great Britain.

a groove in one of said key-ways through which fluid may bypass from one side of said impeller which HENRY F. RADUAZO, Primary Examiner. 

